JP2011100523A - Magnetic recording medium and magnetic recording and playback device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide constitution of a soft magnetic underlayer attaining excellent writing characteristics and reading characteristics to a magnetic recording medium by a magnetic head. <P>SOLUTION: In the magnetic recording medium wherein the soft magnetic underlayer 2 formed by antiferromagnetically bonding a plurality of soft magnetic layers 2a using a spacer layer 2b and a perpendicular magnetic layer 4 whose easily magnetized axis is mainly vertically oriented to a non-magnetic substrate 1 are layered on the non-magnetic substrate 1, the soft magnetic underlayer 2 is constituted of a material having &ge;1.8T saturation magnetic flux density, the product of saturation magnetization of the plurality of antiferromagnetically bonded soft magnetic layers and the sum total layer thickness is specified to be in a range of 2 to 5 (emu/cm<SP>2</SP>) and antiferromagnetic bond is performed in a range of 30 to 70% of the maximum peak of antiferromagnetically bonding force changed by the thickness of the spacer layer 2b interposed between the plurality of soft magnetic layers 2a. The soft magnetic layers have an atomic ratio of Fe:Co of 40:60 to 70:30. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a magnetic recording medium and a magnetic recording / reproducing apparatus.

  The recording density of a hard disk drive (HDD), which is a kind of magnetic recording / reproducing apparatus, is currently increasing by 1.5 times or more per year, and it is said that this trend will continue in the future. Along with this, development of magnetic heads and magnetic recording media suitable for high recording density is underway.

  Currently, a magnetic recording medium mounted on a commercially available magnetic recording / reproducing apparatus is a so-called perpendicular magnetic recording medium in which an easy axis of magnetization in a magnetic film is oriented mainly vertically. Even when the recording density of the perpendicular magnetic recording medium is increased, the influence of the demagnetizing field in the boundary region between the recording bits is small and a clear bit boundary is formed, so that an increase in noise can be suppressed. In addition, since the recording bit volume decreases with the increase in recording density, the thermal fluctuation effect is strong. For this reason, in recent years, much attention has been paid and a medium structure suitable for perpendicular magnetic recording has been proposed.

  In order to meet the demand for higher recording density of magnetic recording media, it has been studied to use a single-pole head having excellent writing ability for the perpendicular magnetic layer. In order to deal with such a single magnetic pole head, a soft magnetic underlayer made of a soft magnetic material is provided between a perpendicular magnetic layer as a recording layer and a nonmagnetic substrate. A so-called two-layer magnetic recording medium has been proposed in which the efficiency of magnetic flux entry and exit between the two is improved.

  In other words, this two-layer magnetic recording medium has a function of increasing the recording magnetic field gradient by spatially concentrating the recording magnetic field by strengthening the recording magnetic field from the main magnetic pole of the magnetic recording head by the mirror image effect of the soft magnetic underlayer. There is.

  However, simply using a magnetic recording medium provided with a soft magnetic underlayer is not satisfactory in recording / reproduction characteristics, thermal fluctuation resistance, and recording resolution at the time of recording / reproduction. A magnetic recording medium excellent in these characteristics is not available. It is requested.

  For example, in Patent Document 1, in a perpendicular magnetic recording medium in which a perpendicular magnetic film is provided on a nonmagnetic substrate via a soft magnetic underlayer, the soft magnetic underlayer is antiferromagnetically coupled using a spacer layer. Perpendicular magnetic recording that prevents leakage magnetic flux generated from the magnetic wall of the soft magnetic underlayer from flowing into the read head and fixes the magnetic wall existing in the soft magnetic underlayer so that it does not move easily, and has low noise characteristics The realization of the medium is described.

  In Patent Document 2, a soft magnetic layer is formed of a plurality of layers, and a separation layer is provided between the soft magnetic layers, thereby increasing the permeability of the soft magnetic layer and leaking the magnetization transition region of the magnetic recording layer. It is described that a magnetic field or a magnetic field from a magnetic head is drawn into a soft magnetic layer, the magnetism recorded in the magnetic recording layer is stabilized, and a writing magnetic field from the magnetic head is more effectively drawn out.

JP 2001-331920 A JP 2001-250223 A

  In the above-described magnetic recording / reproducing apparatus using the perpendicular magnetic recording medium, leakage magnetic flux generated from the magnetic wall of the soft magnetic underlayer is prevented from flowing into the magnetic head, and the domain wall existing in the soft magnetic underlayer is easily formed. In order to fix it so as not to move and to realize low noise characteristics, the soft magnetic underlayer is composed of a plurality of layers, and each layer is antiferromagnetically coupled. In other words, by antiferromagnetically coupling adjacent soft magnetic layers via the spacer layer, the magnetic field received by the magnetic head due to the residual magnetization of the plurality of soft magnetic layers becomes weaker when viewed from the entire soft magnetic layer, and the soft layer of a single layer The generation of noise can be reduced compared to the case where a magnetic layer is used. As the film thickness of the spacer layer at that time, if the thinnest film thickness is selected among the film thicknesses where the antiferromagnetic coupling force periodically peaks, the antiferromagnetic coupling can be strengthened most and the above-mentioned Excellent in achieving purpose.

  Further, the soft magnetic underlayer plays a part of the write head function. In this case, the higher the value of the product Ms · t of the saturation magnetization (Ms) and the film thickness (t) using a material having a high saturation magnetic flux density (Bs) for the soft magnetic underlayer, the higher the writing ability and the higher. Information can be written to a magnetic recording medium having a coercive force. However, if the value of Ms · t is too high, noise generated from the soft magnetic underlayer increases. Conversely, if Ms · t is too low, sufficient magnetic recording on the magnetic recording medium cannot be performed. In addition, the film thickness t of the soft magnetic backing layer is preferably made small from the viewpoint of productivity, scratch resistance, corrosion resistance, and space loss with the magnetic head. That is, when the soft magnetic underlayer is thick, it takes a long time to form the film, and the productivity of the magnetic recording medium is reduced. In addition, soft magnetic materials generally have low hardness and the soft magnetic underlayer is thick. The scratch resistance on the surface of the medium is reduced, the corrosion resistance is reduced by increasing the volume of the soft magnetic layer, and the average distance between the magnetic head and the soft magnetic underlayer is increased, resulting in an increase in the spacing loss.

  It is also important to increase the magnetic permeability of the soft magnetic underlayer. In other words, the leakage magnetic field in the magnetization transition region of the magnetic recording layer and the magnetic field from the magnetic head are drawn into the soft magnetic layer, the magnetism recorded in the magnetic recording layer is stabilized, and the write magnetic field from the magnetic head is more effectively This is because it is necessary to increase the magnetic permeability of the soft magnetic underlayer in order to draw out. Here, iron-based alloys and cobalt-based alloys are generally used as soft magnetic materials, but iron-based alloys have high saturation magnetic flux density and low magnetic permeability, while cobalt-based alloys have high magnetic permeability but saturation magnetic flux density. Is low.

As described above, the soft magnetic underlayer is required to have many roles. However, the conditions for antiferromagnetic coupling of the soft magnetic layer do not necessarily match the conditions for increasing the magnetic permeability of the soft magnetic underlayer. It does not agree with the condition for increasing the saturation magnetic flux density.
The present invention has been proposed in view of such conventional circumstances, and an object of the present invention is to provide a structure of a soft magnetic underlayer that realizes a magnetic recording medium having excellent writing characteristics and reading characteristics by a magnetic head. And

The inventor of the present application has studied to solve the above problems, and as a result, the soft magnetic film is made thinner by increasing the Bs of the material constituting the soft magnetic film. By antiferromagnetic coupling within the range of 30% to 70%, it is possible to achieve both the writing characteristics and reading characteristics of the magnetic recording medium by the magnetic head, and particularly the writing characteristics by using a high Bs material. It has been found that it is possible to improve both the magnetic permeability for high frequency signals by reducing the antiferromagnetic coupling force, and to provide a magnetic recording medium suitable for high signal responsiveness to high frequency signals and high recording density. It was. In addition, it has been found that the magnetic recording medium of the present invention has excellent characteristics from the viewpoints of productivity, scratch resistance, and sparging loss with the magnetic head, thereby completing the present invention.
That is, the present invention provides the following configuration.

(1) A soft magnetic underlayer in which a plurality of soft magnetic layers are antiferromagnetically coupled with a spacer layer on at least a nonmagnetic substrate, and a perpendicular in which an easy axis of magnetization is oriented perpendicularly to the nonmagnetic substrate. The soft magnetic underlayer is composed of a material having a saturation magnetic flux density (Bs) of 1.8 T or more, and is formed of a plurality of soft magnetic layers that are antiferromagnetically coupled. The product (Ms · t) of the saturation magnetization (Ms) and the total layer thickness (t) is in the range of ^{2 to} 5 (emu / cm ² ), and the spacer layer sandwiched between the plurality of soft magnetic layers 1. A magnetic recording medium characterized in that antiferromagnetic coupling is performed within a range of 30% to 70% of the maximum peak of antiferromagnetic coupling force that varies with thickness.
(2) The magnetic recording medium according to (1), wherein the soft magnetic layer contains Fe: Co in a range of 40:60 to 70:30 (atomic ratio).
(3) The magnetic recording medium according to (1) or (2), wherein the thickness of one layer of the soft magnetic underlayer is in the range of 10 nm to 80 nm.
(4) The soft magnetic layer further includes any one selected from the group consisting of Ta, Nb, Zr, and Cr in the range of 1 to 8 atomic%. The magnetic recording medium described.
(5) A magnetic recording / reproducing apparatus comprising: the magnetic recording medium according to any one of (1) to (4); and a magnetic head for recording / reproducing information with respect to the magnetic recording medium.

  As described above, the magnetic recording medium of the present invention has the effects that a high recording density, high-speed writing, and excellent electromagnetic conversion characteristics can be realized. Further, the magnetic recording medium of the present invention has the effect of being excellent in productivity, scratch resistance and corrosion resistance.

It is a characteristic view showing the relationship between the thickness of the Ru layer of the soft magnetic underlayer and the antiferromagnetic coupling force. It is sectional drawing which shows an example of the magnetic recording medium to which this invention is applied. It is sectional drawing which expands and shows the laminated structure of a magnetic layer and a nonmagnetic layer. It is a perspective view which shows an example of a magnetic recording / reproducing apparatus.

Hereinafter, a magnetic recording medium and a magnetic recording / reproducing apparatus to which the present invention is applied will be described in detail with reference to the drawings.
In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Make it not exist.

The magnetic recording medium of the present invention comprises a soft magnetic underlayer in which a plurality of soft magnetic layers are antiferromagnetically coupled by a spacer layer on at least a nonmagnetic substrate, and an easy axis of magnetization mainly with respect to the nonmagnetic substrate. A magnetic recording medium in which perpendicularly oriented perpendicular magnetic layers are laminated, wherein the soft magnetic underlayer is made of a material having a saturation magnetic flux density (Bs) of 1.8 T or more and is antiferromagnetically coupled. The product (Ms · t) of the saturation magnetization (Ms) and the total layer thickness (t) of the soft magnetic layer is in the range of ^{2 to} 5 (emu / cm ² ), and between the plurality of soft magnetic layers The antiferromagnetic coupling is performed within a range of 30% to 70% of the maximum peak of the antiferromagnetic coupling force that varies depending on the thickness of the sandwiched spacer layer.

  As described above, the conditions for antiferromagnetic coupling of a plurality of soft magnetic layers do not necessarily match the conditions for increasing the magnetic permeability of the soft magnetic underlayer, and also do not match the conditions for increasing the saturation magnetic flux density. That is, there is no direct relationship between the antiferromagnetic coupling condition of the soft magnetic layer and the magnetic permeability of the soft magnetic layer. If the antiferromagnetic coupling of the soft magnetic layer increases, the magnetic permeability of the soft magnetic layer does not increase. Absent. As a result, the soft magnetic underlayer of the conventional magnetic recording medium considers only high antiferromagnetic coupling, and does not necessarily consider increasing the magnetic permeability and saturation magnetic flux density of the soft magnetic layer.

  Therefore, in the present invention, focusing on the high-frequency response of the soft magnetic underlayer and the low noise characteristics of the magnetic recording medium, a soft magnetic underlayer capable of realizing high recording density, high-speed writing, and excellent electromagnetic conversion characteristics is realized. did. That is, according to the present invention, the soft magnetic layer is made of a material having a saturation magnetic flux density of 1.8 T or more, thereby reducing the thickness of the soft magnetic layer that can provide an appropriate range of Ms · t and reducing the noise of the magnetic recording medium. Realize. In addition, by increasing the antiferromagnetic coupling force increased by this within the range of 30% to 70% of the maximum peak of the antiferromagnetic coupling force that varies depending on the thickness of the spacer layer, the soft magnetic underlayer has a high speed particularly at high frequencies. Realize responsiveness.

First, the antiferromagnetic coupling of the soft magnetic underlayer will be described. For example, a spacer layer made of Ru is sandwiched between two layers of 46Fe-46Co-5Zr-3B (numbers are atomic%, the same shall apply hereinafter) soft magnetic layer, and the thickness of this spacer layer and the antiferromagnetic coupling force of the soft magnetic layer The result of investigating the relationship is shown in FIG.
As shown in FIG. 1, the antiferromagnetic coupling force of the soft magnetic layer varies depending on the Ru layer thickness, and as the Ru layer thickness is gradually increased, the first peak (reference A) ), Followed by the second peak (reference B) and the third and subsequent peaks (not shown).

  Usually, a magnetic recording medium uses a soft magnetic underlayer that is antiferromagnetically coupled under the condition of the first peak. However, in the present invention, in order to improve the high frequency response of the soft magnetic underlayer, the first peak The soft magnetic film is antiferromagnetically coupled within a range of 30% to 70% of the maximum antiferromagnetic coupling force of the first peak at the shoulder portions (reference numerals C1, C2). Here, when the antiferromagnetic coupling force of the soft magnetic film is greater than 70%, the magnetic permeability of the soft magnetic underlayer to the high frequency signal is lowered, the responsiveness is deteriorated, the writing characteristics of the magnetic recording medium are deteriorated, and the antiferromagnetic property is deteriorated. When the coupling force is less than 30%, the leakage magnetic field from the soft magnetic underlayer is increased, and the reading characteristics of the magnetic recording medium are deteriorated. In the present invention, by setting the antiferromagnetic coupling force of the soft magnetic underlayer to be within a range of 30% to 70% with respect to the maximum value, excellent writing characteristics and reading characteristics to the magnetic recording medium by the magnetic head can be obtained. Can be realized. Here, at the shoulder portion of the first peak, there are two places C1 and C2, as shown in FIG. In the present invention, any of these two conditions can be used, but generally, the change amount of the antiferromagnetic coupling force with respect to the change in the Ru film thickness is smaller on the C2 side (see FIG. 1). The slope of the graph is gradual), the Ru film thickness can be easily controlled, and a magnetic recording medium with stable electromagnetic conversion characteristics can be easily manufactured.

In the present invention, in order to reduce the thickness of the soft magnetic underlayer and increase the antiferromagnetic coupling force formed by the plurality of soft magnetic layers, the saturation magnetic flux density of the soft magnetic material constituting the soft magnetic layer is 1.8 T or more. To do. Examples of soft magnetic materials that can be used in the present invention include FeCo alloys (FeCo, FeCoV, etc.), FeNi alloys (FeNi, FeNiMo, FeNiCr, FeNiSi, etc.), FeAl alloys (FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRu, etc.), FeCr alloys (FeCr, FeCrTi, FeCrCu, etc.), FeTa alloys (FeTa, FaTaC, etc.), FeC alloys, FeN alloys, FeSi alloys, FeP alloys, FeNb alloys, FeHf alloys, and alloys thereof Examples thereof include known ones having a granular structure in which the fine crystals are dispersed in a matrix. In particular, a high saturation magnetic flux density can be realized by using an alloy containing Fe: Co in the range of 40:60 to 70:30 (atomic ratio), and a plurality of antiferromagnetically coupled materials using this material. The soft magnetic layer can be made thin, and the product (Ms · t) of the saturation magnetization (Ms) and the total layer thickness (t) is 2 to 5 (emu / cm ² ). It is possible to realize a magnetic recording medium that is within the range and can obtain high frequency response of the soft magnetic underlayer and low noise characteristics of the magnetic recording medium.

In particular, in the present invention, the above effect can be enhanced most by setting the thickness of one soft magnetic underlayer within the range of 10 nm to 80 nm.
In the present invention, the FeCo alloy-based soft magnetic layer is further added with any one selected from the group consisting of Ta, Nb, Zr, and Cr in the range of 1 to 8 atomic%, thereby forming the soft magnetic underlayer. Magnetic permeability can be increased and corrosion resistance can be increased.

  FIG. 2 shows an example of a magnetic recording medium to which the present invention is applied. As shown in FIG. 2, the magnetic recording medium includes a soft magnetic underlayer 2 including two soft magnetic layers 2a antiferromagnetically coupled by a spacer layer 2b on a nonmagnetic substrate 1, and an orientation control layer 3. A perpendicular magnetic layer 4, a protective layer 5, and a lubricating layer 6 are sequentially stacked.

  In this example of the magnetic recording medium, the perpendicular magnetic layer 4 includes three layers from the non-magnetic substrate 1 side: a lower magnetic layer 4a, an intermediate magnetic layer 4b, and an upper magnetic layer 4c. By including nonmagnetic layers 7a and 7b between the layer 4a and the magnetic layer 4b or between the magnetic layer 4b and the magnetic layer 4c, the magnetic layers 4a to 4c and the nonmagnetic layers 7a and 7b are alternately stacked. Has a structured.

  As the nonmagnetic substrate 1, for example, a metal substrate made of a metal material such as aluminum or an aluminum alloy may be used. For example, a nonmetal substrate made of a nonmetal material such as glass, ceramic, silicon, silicon carbide, or carbon. May be used. In addition, it is also possible to use a substrate in which a NiP layer or a NiP alloy layer is formed on the surface of the metal substrate or nonmetal substrate by using, for example, a plating method or a sputtering method.

  As the glass substrate, for example, amorphous glass or crystallized glass can be used, and as the amorphous glass, for example, general-purpose soda lime glass or aluminosilicate glass can be used. In addition, as the crystallized glass, for example, lithium-based crystallized glass can be used. As the ceramic substrate, for example, general-purpose aluminum oxide, a sintered body mainly composed of aluminum nitride, silicon nitride, or the like, or a fiber reinforced material thereof can be used.

  The nonmagnetic substrate 1 preferably has an average surface roughness (Ra) of 2 nm (20 mm) or less, preferably 1 nm or less from the viewpoint of suitable for high recording density recording with a magnetic head flying low. Further, it is preferable that the surface fine waviness (Wa) is 0.3 nm or less (more preferably 0.25 nm or less) from the viewpoint of being suitable for high recording density recording with the magnetic head flying low. In addition, it is possible to use a magnetic head having a chamfered portion at the end face and a surface average roughness (Ra) of at least one of the side surface portion of 10 nm or less (more preferably 9.5 nm or less). Preferred for stability. In addition, microwaviness (Wa) can be measured as surface average roughness in a measuring range of 80 μm, for example, using a surface roughness measuring device P-12 (manufactured by KLM-Tencor).

  Further, when the nonmagnetic substrate 1 is in contact with the soft magnetic underlayer 2 mainly composed of Co or Fe, there is a possibility that the corrosion progresses due to the adsorption gas on the surface, the influence of moisture, the diffusion of the substrate components, and the like. is there. In this case, it is preferable to provide an adhesion layer between the nonmagnetic substrate 1 and the soft magnetic underlayer 2, thereby suppressing these. In addition, as a material of the adhesion layer, for example, Cr, Cr alloy, Ti, Ti alloy, or the like can be selected as appropriate. The thickness of the adhesion layer is preferably 2 nm (30 mm) or more.

As described above, the soft magnetic underlayer 2 is preferably made of a material containing Fe: Co in the range of 40:60 to 70:30 (atomic ratio), and Ta, Nb in order to increase its magnetic permeability and corrosion resistance. It is preferable to contain any one selected from the group consisting of Zr and Cr in the range of 1 to 8 atomic%.
The soft magnetic underlayer 2 of the present invention is a shoulder portion of the first peak of the antiferromagnetic coupling force that varies depending on the thickness of the spacer layer 2b sandwiched between the plurality of soft magnetic layers 2a. The soft magnetic film is antiferromagnetically coupled within the range of 30% to 70% of the maximum antiferromagnetic coupling force. Further, the magnetic permeability of the soft magnetic underlayer 2 is preferably 1000 H / m or more, more preferably 1000 to 3000 H / m.

  As the spacer layer 2b, Ru, Re, Cu, or the like can be used. Among these, it is particularly preferable to use Ru. Since the Ru film has the strongest antiferromagnetic coupling force (first peak) at about 6 Å (0.6 nm), the first peak shoulder portion is the first peak as in the present invention. In order to antiferromagnetically couple the soft magnetic film within the range of 30% to 70% of the peak maximum antiferromagnetic coupling force, the film thickness of the Ru film is set to the left side of the first peak shown in FIG. When using the shoulder (reference numeral C1), it is 4.2 to 4.9 inches, and when using the right shoulder (reference numeral C2), the distance is 7.1 to 8.8 inches.

  The coercive force Hc of the soft magnetic underlayer 2 is preferably 100 Oe or less (preferably 20 Oe or less). 1 Oe is 79 A / m. When the coercive force Hc exceeds the above range, the soft magnetic characteristics are insufficient, and the reproduced waveform is changed from a so-called rectangular wave to a distorted waveform, which is not preferable.

  In the present invention, when the soft magnetic layer 2a on the upper layer (perpendicular magnetic layer 4) side is formed by sputtering, it is preferable to apply a negative bias to the nonmagnetic substrate 1 in the range of −150 to −400V. When a negative bias is applied to the nonmagnetic substrate 1, Ru or the like of the spacer layer 2b is slightly diffused into the soft magnetic layer 2a, and the coupling between the two soft magnetic layers 2a is strengthened to obtain a more stable AFC coupling. Can do.

  The outermost surface (surface on the orientation control layer 3 side) of the soft magnetic underlayer 2 is preferably formed by partially or completely oxidizing the material constituting the soft magnetic underlayer 2. For example, the material constituting the soft magnetic underlayer 2 is partially oxidized on the surface of the soft magnetic underlayer 2 (surface on the orientation control layer 3 side) and its vicinity, or an oxide of the above material is formed. Are preferably arranged. Thereby, since the magnetic fluctuation of the surface of the soft magnetic underlayer 2 can be suppressed, the noise caused by the magnetic fluctuation can be reduced and the recording / reproducing characteristics of the magnetic recording medium can be improved.

  Further, the orientation control layer 3 formed on the soft magnetic underlayer 2 can improve the recording / reproducing characteristics by refining the crystal grains of the perpendicular magnetic layer 4. Such a material is not particularly limited, but a material having an hcp structure, an fcc structure, or an amorphous structure is preferable. In particular, Ru-based alloys, Ni-based alloys, Co-based alloys, Pt-based alloys, and Cu-based alloys are preferable, and these alloys may be multilayered. For example, it is preferable to adopt a multilayer structure of Ni-based alloy and Ru-based alloy, a multilayer structure of Co-based alloy and Ru-based alloy, or a multilayer structure of Pt-based alloy and Ru-based alloy from the substrate side.

  For example, in the case of a Ni-based alloy, it is made of at least one material selected from NiW alloy, NiTa alloy, NiNb alloy, NiTi alloy, NiZr alloy, NiMn alloy, and NiFe alloy containing 33 to 96 atomic% of Ni. It is preferable. Further, it may be a nonmagnetic material containing 33 to 96 atomic% of Ni and containing at least one or more of Sc, Y, Ti, Zr, Hf, Nb, Ta, and C. In this case, in order to maintain the effect as the orientation control layer 3 and to have a range without magnetism, the Ni content is preferably in the range of 33 atomic% to 96 atomic%.

  In the magnetic recording medium of this embodiment, the thickness of the orientation control layer 3 is preferably 5 to 40 nm (preferably 8 to 30 nm) in the case of a multilayer. When the thickness of the orientation control layer 3 is within the above range, the perpendicular orientation of the perpendicular magnetic layer 4 is particularly high, and the distance between the magnetic head and the soft magnetic underlayer 2 during recording can be reduced. The recording / reproducing characteristics can be improved without reducing the signal resolution.

  On the other hand, if the thickness of the orientation control layer 3 is less than the above range, the perpendicular orientation in the perpendicular magnetic layer 4 is lowered, and the recording / reproducing characteristics and the thermal fluctuation resistance are deteriorated. On the other hand, if the thickness of the orientation control layer 3 exceeds the above range, the magnetic particle diameter of the perpendicular magnetic layer 4 is increased, and noise characteristics may be deteriorated. Further, since the distance between the magnetic head and the soft magnetic underlayer 2 at the time of recording becomes large, the resolution of the reproduction signal and the reproduction output are lowered, which is not preferable.

  Since the surface shape of the orientation control layer 3 affects the surface shape of the perpendicular magnetic layer 4 and the protective layer 5, the surface irregularities of the magnetic recording medium are reduced to reduce the flying height of the magnetic head during recording and reproduction. For this, the surface average roughness Ra of the orientation control layer 3 is preferably 2 nm or less. Thereby, the unevenness on the surface of the magnetic recording medium can be reduced, the flying height of the magnetic head during recording and reproduction can be sufficiently lowered, and the recording density can be increased.

  Further, oxygen, nitrogen, or the like may be introduced into the gas for forming the orientation control layer 3. For example, when a sputtering method is used as the film forming method, the process gas is a gas in which oxygen is mixed in an amount of 0.05 to 50% (preferably 0.1 to 20%) by volume with argon, and nitrogen is added to argon. Is preferably used in a volume ratio of 0.01 to 20% (preferably 0.02 to 10%).

Further, the orientation control layer 3 may have a structure in which metal particles are dispersed in an oxide, a metal nitride, or a metal carbide. In order to obtain such a structure, it is preferable to use an alloy material containing an oxide, a metal nitride, or a metal carbide. Specifically, as the oxide, for example, SiO ₂ , Al ₂ O ₃ , Ta ₂ O ₅ , Cr ₂ O ₃ , MgO, Y ₂ O ₃ , TiO _2, etc. As the metal nitride, for example, AlN, Si For example, TaC, BC, SiC, or the like can be used as the metal carbide such as ₃ N ₄ , TaN, or CrN. Furthermore, for example, NiTa—SiO ₂ , RuCo—Ta ₂ O ₅ , Ru—SiO ₂ , Pt—Si ₃ N ₄ , Pd—TaC, or the like can be used.

  The content of the oxide, metal nitride, or metal carbide in the orientation control layer 3 is preferably 1 mol% or more and 12 mol% or less with respect to the alloy. When the content of oxide, metal nitride, or metal carbide in the orientation control layer 3 exceeds the above range, the oxide, metal nitride, or metal carbide remains in the metal particles, and the crystallinity of the metal particles and In addition to impairing the orientation, the crystallinity and orientation of the magnetic layer formed on the orientation control layer 3 may be impaired. Moreover, when the content of the oxide, metal nitride, or metal carbide in the orientation control layer 3 is less than the above range, it is not preferable because the effect of addition of the oxide, metal nitride, or metal carbide cannot be obtained. .

  Further, it may be preferable to provide a nonmagnetic underlayer 8 between the orientation control layer 3 and the perpendicular magnetic layer 4. In the initial part of the perpendicular magnetic layer 4 immediately above the orientation control layer 3, disorder of crystal growth is likely to occur, which causes noise. The occurrence of noise can be suppressed by replacing the disturbed portion of the initial portion with the nonmagnetic underlayer 8.

The nonmagnetic underlayer 8 is preferably made of a material containing Co as a main component and further containing an oxide 41. The Cr content is preferably 25 atomic% (atomic%) or more and 50 atomic% or less. As the oxide 41, for example, an oxide such as Cr, Si, Ta, Al, Ti, Mg, and Co is preferably used, and among them, TiO ₂ , Cr ₂ O ₃ , SiO _{2 and the} like are preferably used. Can do. The content of the oxide is preferably 3 mol% or more and 18 mol% or less with respect to the total amount of mol calculated as one compound, for example, an alloy such as Co, Cr, and Pt constituting the magnetic particles.

The nonmagnetic underlayer 8 is preferably made of a complex oxide to which two or more kinds of oxides are added. Among these, Cr ₂ O ₃ —SiO ₂ , Cr ₂ O ₃ —TiO ₂ , Cr ₂ O ₃ —SiO ₂ —TiO _{2 and the} like can be preferably used. Furthermore, CoCr—SiO ₂ , CoCr—TiO ₂ , CoCr—Cr ₂ O ₃ —SiO ₂ , CoCr—TiO ₂ —Cr ₂ O ₃ , CoCr—Cr ₂ O ₃ —TiO ₂ —SiO ₂ or the like is preferably used. Can do. Further, Pt may be added from the viewpoint of crystal growth.

  The thickness of the nonmagnetic underlayer 8 is preferably 0.2 nm or more and 3 nm or less. If the thickness exceeds 3 nm, Hc and Hn decrease, which is not preferable.

The magnetic layer 4a is made of a material containing Co as a main component and further containing an oxide 41. As the oxide 41, for example, an oxide such as Cr, Si, Ta, Al, Ti, Mg, Co is used. Is preferred. Among _{them, TiO 2, Cr 2 O 3} , SiO ₂ or the like can be suitably used. The magnetic layer 4a is preferably made of a complex oxide to which two or more kinds of oxides are added. Among these, Cr ₂ O ₃ —SiO ₂ , Cr ₂ O ₃ —TiO ₂ , Cr ₂ O ₃ —SiO ₂ —TiO _{2 and the} like can be preferably used.

  In the magnetic layer 4a, it is preferable that magnetic particles (crystal grains having magnetism) 42 are dispersed in the layer. Further, as shown in FIG. 3, the magnetic particles 42 preferably have a columnar structure that penetrates the magnetic layers 4a and 4b and further the magnetic layer 4c vertically. By having such a structure, the orientation and crystallinity of the magnetic particles 42 of the magnetic layer 4a are improved, and as a result, a signal / noise ratio (S / N ratio) suitable for high-density recording can be obtained. .

  In order to obtain such a structure, the amount of the oxide 41 to be contained and the film formation conditions of the magnetic layer 4a are important. That is, the content of the oxide 41 is 3 mol% or more and 18 mol% or less with respect to the total mol amount of the magnetic particles 42, for example, an alloy such as Co, Cr, and Pt calculated as one compound. preferable. More preferably, it is 6 mol% or more and 13 mol% or less.

  The above range is preferable as the content of the oxide 41 in the magnetic layer 4a. When the magnetic layer 4a is formed, the oxide 41 is precipitated around the magnetic particles 42, and the magnetic particles 42 are isolated and refined. This is because it becomes possible. On the other hand, when the content of the oxide 41 exceeds the above range, the oxide 41 remains in the magnetic particle 42, impairs the orientation and crystallinity of the magnetic particle 42, and further above and below the magnetic particle 42. The oxide 41 is deposited, and as a result, a columnar structure in which the magnetic particles 42 penetrate through the magnetic layers 4a to 4c is not formed. In addition, when the content of the oxide 41 is less than the above range, separation and refinement of the magnetic particles 42 are insufficient, resulting in an increase in noise during recording and reproduction, and a signal / This is not preferable because the noise ratio (S / N ratio) cannot be obtained.

  The content of Cr in the magnetic layer 4a is preferably 4 atom% or more and 19 atom% or less (more preferably 6 atom% or more and 17 atom% or less). The reason why the Cr content is in the above range is that the magnetic anisotropy constant Ku of the magnetic particles 42 is not lowered too much, and high magnetization is maintained. As a result, recording / reproduction characteristics suitable for high-density recording and sufficient heat This is because fluctuation characteristics can be obtained.

  On the other hand, when the Cr content exceeds the above range, the magnetic anisotropy constant Ku of the magnetic particles 42 becomes small, so that the thermal fluctuation characteristics deteriorate, and the crystallinity and orientation of the magnetic particles 42 deteriorate. As a result, the recording / reproduction characteristics deteriorate, which is not preferable. Further, when the Cr content is less than the above range, the magnetic anisotropy constant Ku of the magnetic particles 42 is high, so that the perpendicular coercive force becomes too high and data is sufficiently written by a magnetic head when data is recorded. This is not preferable because the recording characteristics (OW) are unsuitable for high density recording.

  The content of Pt in the magnetic layer 4a is preferably 8 atom% or more and 20 atom% or less. The reason why the Pt content is within the above range is that the magnetic anisotropy constant Ku required for the perpendicular magnetic layer 4 is low when it is less than 8 atomic%. On the other hand, when it exceeds 20 atomic%, a stacking fault occurs inside the magnetic particle 42, and as a result, the magnetic anisotropy constant Ku decreases. Therefore, in order to obtain thermal fluctuation characteristics and recording / reproduction characteristics suitable for high-density recording, the Pt content is preferably set in the above range.

  In addition, when the Pt content exceeds the above range, an fcc structure layer is formed in the magnetic particles 42, and the crystallinity and orientation may be impaired. On the other hand, if the Pt content is less than the above range, the magnetic anisotropy constant Ku for obtaining thermal fluctuation characteristics suitable for high-density recording cannot be obtained.

  In addition to Co, Cr, Pt and oxide 41, the magnetic layer 4a contains one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re. Can be included. By including the above elements, the miniaturization of the magnetic particles 42 can be promoted or the crystallinity and orientation can be improved, and recording / reproduction characteristics and thermal fluctuation characteristics suitable for higher density recording can be obtained.

  Further, the total content of the above elements is preferably 8 atomic% or less. If it exceeds 8 atomic%, a phase other than the hcp phase is formed in the magnetic particles 42, so that the crystallinity and orientation of the magnetic particles 42 are disturbed. As a result, recording / reproduction characteristics and thermal fluctuation suitable for high density recording are obtained. Since characteristics cannot be obtained, it is not preferable.

As a material suitable for the magnetic layer 4a, for example, 90 (Co14Cr18Pt) -10 (SiO ₂ ) {Cr content of 14 atomic%, Pt content of 18 atomic%, and the balance Co were calculated as one compound. Molar concentration is 90 mol%, oxide composition composed of SiO ₂ is 10 mol%}, 92 (Co10Cr16Pt) -8 (SiO ₂ ), 94 (Co8Cr14Pt4Nb) -6 (Cr ₂ O ₃ ), and (CoCrPt)-(Ta _{2 O 5), (CoCrPt)} - (Cr 2 O 3) - (TiO 2), (CoCrPt) - (Cr 2 O 3) - (SiO 2), (CoCrPt) - (Cr 2 O 3) - (SiO _{2) - (TiO 2),} (CoCrPtMo) - (TiO), (CoCrPtW) - (TiO 2), (CoCrPtB) - (Al 2 O ₃ ), (CoCrPtTaNd) — (MgO), (CoCrPtBCu) — (Y ₂ O ₃ ), (CoCrPtRu) — (SiO ₂ ), and the like.

The magnetic layer 4b is preferably made of a material containing Co as a main component and further containing an oxide 41. The oxide 41 is preferably an oxide of Cr, Si, Ta, Al, Ti, Mg, and Co. Of these, TiO ₂ , Cr ₂ O ₃ , and SiO ₂ can be preferably used. The magnetic layer 4b is preferably made of a composite oxide to which two or more types of oxides 41 are added. Among these, Cr ₂ O ₃ —SiO ₂ , Cr ₂ O ₃ —TiO ₂ , Cr ₂ O ₃ —SiO ₂ —TiO _{2 and the} like can be preferably used.

  In the magnetic layer 4b, it is preferable that magnetic particles (crystal particles having magnetism) 42 are dispersed in the layer. As shown in FIG. 3, the magnetic particles 42 preferably have a columnar structure that penetrates the magnetic layers 4a and 4b and the magnetic layer 4c vertically. By forming such a structure, the orientation and crystallinity of the magnetic particles 42 of the magnetic layer 4b are improved, and as a result, a signal / noise ratio (S / N ratio) suitable for high-density recording can be obtained. it can.

  The content of the oxide 41 in the magnetic layer 4b is preferably 3 mol% or more and 18 mol% or less with respect to the total amount of compounds such as Co, Cr, and Pt constituting the magnetic particles 42. More preferably, it is 6 mol% or more and 13 mol% or less.

  The above range is preferable as the content of the oxide 41 in the magnetic layer 4b. When the magnetic layer 4b is formed, the oxide 41 is precipitated around the magnetic particles 42, and the magnetic particles 42 are isolated and refined. This is because it becomes possible. On the other hand, when the content of the oxide 41 exceeds the above range, the oxide 41 remains in the magnetic particle 42, impairs the orientation and crystallinity of the magnetic particle 42, and further above and below the magnetic particle 42. The oxide 41 is deposited, and as a result, a columnar structure in which the magnetic particles 42 penetrate through the magnetic layers 4a to 4c is not formed. Further, when the content of the oxide 41 is less than the above range, separation and refinement of the magnetic particles 42 are insufficient, resulting in an increase in noise during recording / reproduction, and a signal / This is not preferable because the noise ratio (S / N ratio) cannot be obtained.

  The content of Cr in the magnetic layer 4b is preferably 4 atom% or more and 18 atom% or less (more preferably 8 atom% or more and 15 atom% or less). The reason why the Cr content is in the above range is that the magnetic anisotropy constant Ku of the magnetic particles 42 is not lowered too much, and high magnetization is maintained, resulting in recording / reproduction characteristics suitable for high-density recording and sufficient heat. This is because fluctuation characteristics can be obtained.

  On the other hand, when the Cr content exceeds the above range, the magnetic anisotropy constant Ku of the magnetic particles 42 becomes small, so that the thermal fluctuation characteristics deteriorate, and the crystallinity and orientation of the magnetic particles 42 deteriorate. As a result, the recording / reproduction characteristics deteriorate, which is not preferable. Further, when the Cr content is less than the above range, the magnetic anisotropy constant Ku of the magnetic particles 42 is high, so that the perpendicular coercive force becomes too high and data is sufficiently written by a magnetic head when data is recorded. This is not preferable because the recording characteristics (OW) are unsuitable for high density recording.

  The content of Pt in the magnetic layer 4b is preferably 10 atomic percent or more and 22 atomic percent or less. The content of Pt within the above range is less than 10 atomic% because the magnetic anisotropy constant Ku required for the perpendicular magnetic layer 4 is not preferable. On the other hand, if it exceeds 22 atomic%, a stacking fault occurs inside the magnetic particle 42, and as a result, the magnetic anisotropy constant Ku becomes low, which is not preferable. In order to obtain thermal fluctuation characteristics and recording / reproduction characteristics suitable for high-density recording, the Pt content is preferably set in the above range.

  In addition, when the Pt content exceeds the above range, an fcc structure layer is formed in the magnetic particles 42, and the crystallinity and orientation may be impaired. On the other hand, if the Pt content is less than the above range, the magnetic anisotropy constant Ku for obtaining thermal fluctuation characteristics suitable for high-density recording cannot be obtained.

  The magnetic layer 4b includes one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, and Re in addition to Co, Cr, Pt, and the oxide 41. Can be included. By including the above elements, the miniaturization of the magnetic particles 42 can be promoted or the crystallinity and orientation can be improved, and recording / reproduction characteristics and thermal fluctuation characteristics suitable for higher density recording can be obtained.

  Further, the total content of the above elements is preferably 8 atomic% or less. If it exceeds 8 atomic%, a phase other than the hcp phase is formed in the magnetic particles 42, so that the crystallinity and orientation of the magnetic particles 42 are disturbed. As a result, recording / reproduction characteristics and thermal fluctuation suitable for high density recording are obtained. Since characteristics cannot be obtained, it is not preferable.

  The magnetic layer 4c is preferably made of a material that contains Co as a main component and does not contain an oxide. As shown in FIG. 3, the magnetic particles 42 in the layer are columnar from the magnetic particles 42 in the magnetic layer 4a. The structure is preferably epitaxially grown. In this case, the magnetic particles 42 of the magnetic layers 4a to 4c are preferably epitaxially grown in a columnar shape in a one-to-one correspondence in each layer. Further, the magnetic particles 42 of the magnetic layer 4b are epitaxially grown from the magnetic particles 42 in the magnetic layer 4a, so that the magnetic particles 42 of the magnetic layer 4b are miniaturized and the crystallinity and orientation are further improved. Become.

  The content of Cr in the magnetic layer 4c is preferably 10 atomic percent or more and 24 atomic percent or less. By setting the Cr content in the above range, a sufficient output during data reproduction can be ensured, and even better thermal fluctuation characteristics can be obtained. On the other hand, when the content of Cr exceeds the above range, the magnetization of the magnetic layer 4c becomes too small, which is not preferable. When the Cr content is less than the above range, the magnetic particles 42 are not sufficiently separated and refined, noise during recording / reproduction increases, and a signal / noise ratio (S) suitable for high-density recording (S / N ratio) is not obtained.

  The magnetic layer 4c may be made of a material containing Pt in addition to Co and Cr. The content of Pt in the magnetic layer 4c is preferably 8 atom% or more and 20 atom% or less. When the Pt content is in the above range, a sufficient coercive force suitable for high recording density can be obtained, and a high reproduction output during recording and reproduction can be maintained, resulting in recording suitable for high density recording. Reproduction characteristics and thermal fluctuation characteristics can be obtained.

  On the other hand, when the content of Pt exceeds the above range, an fcc-structured phase is formed in the magnetic layer 4c, which is not preferable because the crystallinity and orientation may be impaired. On the other hand, if the Pt content is less than the above range, the magnetic anisotropy constant Ku for obtaining thermal fluctuation characteristics suitable for high-density recording cannot be obtained.

  The magnetic layer 4c contains one or more elements selected from B, Ta, Mo, Cu, Nd, W, Nb, Sm, Tb, Ru, Re, and Mn in addition to Co, Cr, and Pt. Can do. By including the above elements, the miniaturization of the magnetic particles 42 can be promoted or crystallinity and orientation can be improved, and recording / reproduction characteristics and thermal fluctuation characteristics suitable for higher density recording can be obtained.

  The total content of the above elements is preferably 16 atomic% or less. On the other hand, when the content exceeds 16 atomic%, a phase other than the hcp phase is formed in the magnetic particles 42, so that the crystallinity and orientation of the magnetic particles 42 are disturbed. As a result, recording / reproduction suitable for high-density recording is performed. It is not preferable because characteristics and thermal fluctuation characteristics cannot be obtained.

  Examples of suitable materials for the magnetic layer 4c include CoCrPt and CoCrPtB. In the case of the CoCrPtB system, the total content of Cr and B is preferably 18 atom% or more and 28 atom% or less.

  Suitable materials for the magnetic layer 4c include, for example, Co14-24Cr8-22Pt {Cr content 14-24 atomic%, Pt content 8-22 atomic%, balance Co} in CoCrPt series, Co10 in CoCrPtB series. 24Cr8-22Pt0-16B {Cr content 10-24 atom%, Pt content 8-22 atom%, B content 0-16 atom%, balance Co} is preferred. In other systems, in CoCrPtTa system, Co10-24Cr8-22Pt1-5Ta {Cr content 10-24 atom%, Pt content 8-22 atom%, Ta content 1-5 atom%, balance Co}, CoCrPtTaB system Then, Co10-24Cr8-22Pt1-5Ta1-10B {Cr content 10-24 atomic%, Pt content 8-22 atomic%, Ta content 1-5 atomic%, B content 1-10 atomic%, balance Co }, Other materials such as CoCrPtBNd, CoCrPtTaNd, CoCrPtNb, CoCrPtBW, CoCrPtMo, CoCrPtCuRu, and CoCrPtRe may be used.

  The perpendicular coercive force (Hc) of the perpendicular magnetic layer 4 is preferably 3000 [Oe] or more. When the coercive force is less than 3000 [Oe], the recording / reproducing characteristics, particularly the frequency characteristics, are deteriorated, and the thermal fluctuation characteristics are also deteriorated, which is not preferable as a high-density recording medium.

  The reverse magnetic domain nucleation magnetic field (-Hn) of the perpendicular magnetic layer 4 is preferably 1500 [Oe] or more. When the reverse domain nucleation magnetic field (-Hn) is less than 1500 [Oe], the thermal fluctuation resistance is poor, which is not preferable.

  The perpendicular magnetic layer 4 preferably has an average particle diameter of magnetic particles of 3 to 12 nm. This average particle diameter can be obtained, for example, by observing the perpendicular magnetic layer 4 with a TEM (transmission electron microscope) and image-processing the observed image.

  The thickness of the perpendicular magnetic layer 4 is preferably 5 to 20 nm. If the thickness of the perpendicular magnetic layer 4 is less than the above, sufficient reproduction output cannot be obtained, and the thermal fluctuation characteristics also deteriorate. When the thickness of the perpendicular magnetic layer 4 exceeds the above range, the magnetic particles in the perpendicular magnetic layer 4 are enlarged, increasing noise during recording and reproduction, and a signal / noise ratio (S / N). Ratio) and recording / reproducing characteristics represented by recording characteristics (OW) are not preferable.

The protective layer 5 is for preventing corrosion of the perpendicular magnetic layer 4 and preventing damage to the surface of the medium when the magnetic head comes into contact with the medium, and a conventionally known material can be used, for example, C, SiO ₂ and those containing ZrO ₂ can be used. The thickness of the protective layer 5 is preferably 1 to 10 nm from the viewpoint of high recording density because the distance between the head and the medium can be reduced.

  For the lubricating layer 6, it is preferable to use a lubricant such as perfluoropolyether, fluorinated alcohol, fluorinated carboxylic acid, or the like.

  In the present invention, the magnetic layer on the nonmagnetic substrate 1 side is preferably a granular magnetic layer, and the magnetic layer on the protective layer 5 side is preferably a non-granular magnetic layer containing no oxide. With this configuration, it is possible to more easily control and adjust each characteristic such as the thermal fluctuation characteristic, recording characteristic (OW), and S / N ratio of the magnetic recording medium.

  In the present invention, the perpendicular magnetic layer 4 can be composed of four or more magnetic layers. For example, in addition to the magnetic layers 4a and 4b, a magnetic layer having a granular structure is composed of three layers, and a magnetic layer 4c not containing an oxide is provided thereon, and a magnetic layer not containing an oxide is also provided. The layer 4c may have a two-layer structure and be provided on the magnetic layers 4a and 4b.

  In the present invention, it is preferable to provide a nonmagnetic layer 7 (indicated by reference numerals 7a and 7b in FIG. 2) between three or more magnetic layers constituting the perpendicular magnetic layer 4. By providing the nonmagnetic layer 7 with an appropriate thickness, magnetization reversal of individual films can be facilitated, and dispersion of magnetization reversal of the entire magnetic particles can be reduced. As a result, the S / N ratio can be further improved.

  That is, the thickness of the nonmagnetic layer 7 is a range in which the magnetostatic coupling of each layer constituting the perpendicular magnetic layer 4 is not completely broken, specifically 0.1 nm or more and 2 nm or less (more preferably 0.1 or more and 0.8 nm). Or less).

  When the three or more magnetic layers 2a of the present invention are ferromagnetically coupled (ferro coupling coupling, hereinafter referred to as FC coupling) and the magnetostatic coupling is completely broken, the MH loop is Since the loop is reversed in two stages, it can be easily discriminated. When this two-stage loop occurs, it means that the magnetic grains do not reverse all at once with respect to the magnetic field from the magnetic head, and as a result, the S / N ratio at the time of reproduction is significantly deteriorated and the resolution is lowered. Therefore, it is not preferable.

  However, when Ru or a Ru alloy is used, antiferromagnetic coupling occurs in the range of 0.6 nm to 1.2 nm. In the present invention, each magnetic layer 2a is preferably magnetostatically coupled by FC instead of antiferromagnetic coupling.

As the nonmagnetic layer 7 provided between the magnetic layers constituting the perpendicular magnetic layer 4, it is preferable to use a material having an hcp structure. Specifically, for example, Ru, Ru alloy, CoCr alloy, CoCrX ₁ alloy _{(X 1} is, Pt, Ta, Zr, Re , Ru, Cu, Nb, Ni, Mn, Ge, Si, O, N, W , Mo, Ti, V, Zr, or B represents at least one element or two or more elements).

  When a CoCr-based alloy is used as the nonmagnetic layer 7 provided between the magnetic layers constituting the perpendicular magnetic layer 4, the Co content is preferably in the range of 30 to 80 atomic%. This is because within this range, the coupling between the magnetic layers can be adjusted to be small.

  Further, as the nonmagnetic layer 7 provided between the magnetic layers constituting the perpendicular magnetic layer 4, as an alloy having an hcp structure, an alloy such as Ru, Re, Ti, Y, Hf, Zn, or the like can be used other than Ru. .

Further, as the nonmagnetic layer 7 provided between the magnetic layers constituting the perpendicular magnetic layer 4, metals or alloys having other structures may be used as long as the crystallinity and orientation of the upper and lower magnetic layers are not impaired. it can. Specifically, for example, Pd, Pt, Cu, Ag, Au, Ir, Mo, W, Ta, Nb, V, Bi, Sn, Si, Al, C, B, Cr, or an alloy thereof is used. it can. In particular, as a Cr alloy, CrX ₂ (X ₂ represents at least one element selected from Ti, W, Mo, Nb, Ta, Si, Al, B, C, and Zr. ) And the like can be preferably used. In this case, the Cr content is preferably 60 atomic% or more.

As the nonmagnetic layer 7 provided between the magnetic layers constituting the perpendicular magnetic layer 4, it is preferable to use a layer having a structure in which metal particles of the above alloy are dispersed in an oxide, a metal nitride, or a metal carbide. Further, it is more preferable that the metal particles have a columnar structure penetrating the nonmagnetic layer 7 vertically. In order to obtain such a structure, it is preferable to use an alloy material containing an oxide, a metal nitride, or a metal carbide. Specifically, as the oxide, for example, SiO ₂ , Al ₂ O ₃ , Ta ₂ O ₅ , Cr ₂ O ₃ , MgO, Y ₂ O ₃ , TiO _2, etc. As the metal nitride, for example, AlN, Si For example, TaC, BC, SiC, or the like can be used as the metal carbide such as ₃ N ₄ , TaN, or CrN. Furthermore, for example, CoCr—SiO ₂ , CoCr—TiO ₂ , CoCr—Cr ₂ O ₃ , CoCrPt—Ta ₂ O ₅ , Ru—SiO ₂ , Ru—Si ₃ N ₄ , Pd—TaC, and the like can be used.

  The content of the oxide, metal nitride, or metal carbide in the nonmagnetic layer 7 provided between the magnetic layers constituting the perpendicular magnetic layer 4 is a content that does not impair the crystal growth and crystal orientation of the perpendicular magnetic film. Is preferred. In addition, the content of oxide, metal nitride, or metal carbide is preferably 4 mol% or more and 30 mol% or less with respect to the alloy.

  When the content of the oxide, metal nitride, or metal carbide in the nonmagnetic layer 7 exceeds the above range, the oxide, metal nitride, or metal carbide remains in the metal particle, and the metal particle In addition to impairing crystallinity and orientation, oxides, metal nitrides, or metal carbides are also deposited on the top and bottom of the metal particles, making it difficult for the metal particles to have a columnar structure that vertically penetrates the nonmagnetic layer 7. This is not preferable because the crystallinity and orientation of the magnetic layer formed on the magnetic layer 7 may be impaired. On the other hand, when the content of the oxide, metal nitride, or metal carbide in the nonmagnetic layer 7 is less than the above range, the effect of adding the oxide, metal nitride, or metal carbide cannot be obtained. Therefore, it is not preferable.

  FIG. 4 shows an example of a magnetic recording / reproducing apparatus to which the present invention is applied. This magnetic recording / reproducing apparatus includes a magnetic recording medium 50 having the configuration shown in FIG. 2, a medium driving unit 51 that rotationally drives the magnetic recording medium 50, a magnetic head 52 that records and reproduces information on the magnetic recording medium 50, A head driving unit 53 that moves the magnetic head 52 relative to the magnetic recording medium 50 and a recording / reproducing signal processing system 54 are provided. Further, the recording / reproducing signal processing system 54 can process data input from the outside and send a recording signal to the magnetic head 52, process a reproducing signal from the magnetic head 52, and send the data to the outside. ing. Further, as the magnetic head 52 used in the magnetic recording / reproducing apparatus to which the present invention is applied, a magnetic head suitable for a higher recording density having a GMR element utilizing a giant magnetoresistance effect (GMR) as a reproducing element is used. be able to.

  According to the magnetic recording / reproducing apparatus, an excellent magnetic recording / reproducing apparatus can be obtained by adopting a magnetic recording medium having a high recording density, high-speed writing, and excellent electromagnetic conversion characteristics to which the present invention is applied to the magnetic recording medium 50. Can do.

  Hereinafter, the effects of the present invention will be made clearer by examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

Example 1
In Example 1, first, a cleaned glass substrate (manufactured by Konica Minolta Co., Ltd., 2.5 inches in outer diameter) is accommodated in a film forming chamber of a DC magnetron sputtering apparatus (C-3040 made by Anelva Co., Ltd.), and the ultimate vacuum is achieved. After the inside of the film formation chamber was evacuated to 1 × 10 ⁻⁵ Pa, an adhesion layer having a thickness of 10 nm was formed on the glass substrate using a 60Cr-50Ti target. Further, on this adhesion layer, a target of 46Fe-46Co-5Zr-3B {Fe content 46 atomic%, Co content 46 atomic%, Zr content 5 atomic%, B content 3 atomic%} was used. A soft magnetic layer having a layer thickness of 34 nm was formed at a substrate temperature of 100 ° C. or less, and a Ru layer was formed thereon with a layer thickness of 0.76 nm, and then a 46Fe-46Co-5Zr-3B soft magnetic layer was further formed. A film thickness of 34 nm was formed and used as a soft magnetic underlayer.

  In forming the upper soft magnetic underlayer, a negative bias of −200 V was applied to the glass substrate. The soft magnetic material has a saturation magnetic flux density of 1.9T.

Further, the magnetic permeability of this soft magnetic underlayer is 7000 (H / m), Ms · t is 4.6 (emu / cm ² ), and the soft magnetic underlayer has an antiferromagnetic coupling force. It was confirmed with an oscillating magnetic property measuring device (VSM) that antiferromagnetic coupling occurred at 50% of the maximum peak.

  Next, on the soft magnetic underlayer 2, Ni-6W {W content 6 atomic%, remaining Ni} target and Ru target were sequentially formed with a layer thickness of 5 nm and 20 nm, respectively. It was set as the orientation control layer.

Next, on the alignment control layer 3, a magnetic layer of a multilayer structure, Co12Cr16Pt-16TiO ₂ (film thickness _{3nm), Co5Cr22Pt-4SiO 2 -3Cr} 2 O 3 -2TiO 2 ( film thickness 3nm), Ru47.5Co ( thickness _{0.5nm), Co10Cr16Pt3Ru-4SiO 2 -3Cr} 2 O 3 -2TiO 2 ( film thickness _{3nm), Co6Cr16Pt6Ru-4SiO 2 -3Cr} 2 O 3 -2TiO 2 ( film thickness 3nm), Ru47.5Co, Co11.5Cr13Pt10Ru -4SiO ₂ -3Cr ₂ O ₃ -2TiO ₂ (film thickness 3 nm) and Co15Cr16Pt6B (film thickness 3 nm) were stacked.

  Next, a protective layer having a thickness of 2.5 nm was formed by a CVD method, and then a lubricating layer made of perfluoropolyether was formed by a dipping method to obtain a magnetic recording medium of Example 1.

(Comparative Examples 1-9, Examples 2-7)
A magnetic recording medium was manufactured in the same manner as in the example, and the soft magnetic underlayer was configured as shown in Table 1.
(Evaluation of electromagnetic conversion characteristics)

  The magnetic recording / reproducing characteristics of the magnetic recording medium manufactured by the above method were measured using a read / write analyzer (model number: RWA1632; manufactured by GUZIK, USA) and a spin stand (model number: S1701MP). At this time, a magnetic head using a single pole magnetic pole for writing and a TuMR for reading was used as a magnetic head for evaluation.

In this example, the S / N ratio was measured by recording a signal having a recording density of 750 kFCI. As for the recording characteristics (OW), first, a 750 kFCI signal was written, then a 100 kFCI signal was overwritten, a high frequency component was taken out by a frequency filter, and the data writing ability was evaluated by the residual ratio.
(Corrosion resistance evaluation)
In the corrosion resistance evaluation, the magnetic recording medium was kept in an air environment at a temperature of 80 ° C. and a humidity of 85% for 96 hours, and then a 3% nitric acid aqueous solution was added to the surface of the magnetic recording medium at five locations (100 microliter / location), Water was added dropwise at 5 locations (100 microliters / location), allowed to stand for 1 hour and then collected, and the amount of Co contained therein was measured by ICP-MS. In the measurement by ICP-MS, 1 ml of 3% nitric acid containing 200 ppt of Y was used as a reference solution.

(Scratch resistance evaluation)
The scratch resistance of the magnetic recording medium was evaluated using a Kubota Comps SAF tester and a Candela optical surface inspection apparatus (OSA). The measurement conditions at this time were a disk rotation speed of 5000 rpm, an atmospheric pressure of 100 Torr, and a room temperature condition. Further, as a measuring method, the head was loaded for 2000 seconds while being loaded with the SAF tester, and then the number of scratches was measured with OSA.

  Table 1 shows the evaluation results of the magnetic recording media manufactured in Examples 1 to 12 and Comparative Examples 1 to 3. The electromagnetic conversion characteristics (S / N, OW) were evaluated based on the amount of change (dB) from the reference value with the value of Comparative Example 1 as a reference. From these results, the magnetic recording medium of the present invention was excellent in electromagnetic conversion characteristics, as well as corrosion resistance and scratch resistance.

A ... first peak B ... second peak C1 ... left shoulder portion C2 of first peak ... right shoulder portion 1 of first peak ... nonmagnetic substrate
2. Soft magnetic underlayer
2a ... magnetic layer 2b ... spacer layer 3 ... orientation control layer
4 ... perpendicular magnetic layer
4a: lower magnetic layer
4b ... middle magnetic layer
4c ... upper magnetic layer
5 ... Protective layer
6 ... Lubrication layer
7 ... Nonmagnetic layer
8 ... Nonmagnetic underlayer
7a: lower nonmagnetic layer
7b: upper nonmagnetic layer
41 ... Oxides
42 ... Magnetic particles (non-magnetic particles in the layers 7a and 7b)
50. Magnetic recording medium
51. Medium drive unit
52. Magnetic head
53. Head drive unit
54. Recording / reproducing signal processing system

Claims (5)

A soft magnetic underlayer in which a plurality of soft magnetic layers are antiferromagnetically coupled with a spacer layer on at least a nonmagnetic substrate; and a perpendicular magnetic layer whose easy axis is oriented perpendicularly to the nonmagnetic substrate; In which the soft magnetic underlayer is made of a material having a saturation magnetic flux density (Bs) of 1.8 T or more and is anti-ferromagnetically coupled with a plurality of soft magnetization layers (saturation magnetization ( The product (Ms · t) of Ms) and the total layer thickness (t) is in the range of ^{2 to} 5 (emu / cm ² ) and varies depending on the thickness of the spacer layer sandwiched between the plurality of soft magnetic layers. The magnetic recording medium is characterized by being antiferromagnetically coupled within a range of 30% to 70% of the maximum peak of antiferromagnetic coupling force. The magnetic recording medium according to claim 1, wherein the soft magnetic layer contains Fe: Co in a range of 40:60 to 70:30 (atomic ratio). 3. The magnetic recording medium according to claim 1, wherein a thickness of one layer of the soft magnetic underlayer is in a range of 10 nm to 80 nm. 4. The magnetic recording medium according to claim 2, wherein the soft magnetic layer further contains any one selected from the group consisting of Ta, Nb, Zr, and Cr in a range of 1 to 8 atomic%. . 5. A magnetic recording / reproducing apparatus comprising: the magnetic recording medium according to claim 1; and a magnetic head for recording / reproducing information on / from the magnetic recording medium.

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